LC Exam 2 Fertilization and Implantation Flashcards
Sperm head components
Haploid, condensed chromatin
Protamines (specialized histones)
Acrosome
Sperm tail components
9+2 axoneme structure
Kartagener’s -> dyenin dysfxn and no motility
Oocyte suspension
Up to 45 years
Meiotic Prophase 1
As oocyte number decreases so does quality
Zona pellucida
Barrier - egg not exposed to environment until rupture
Glycoprotein sheet: ZP1, ZP2, ZP3
Mostly protein
Sperm bind to ZP
Mutations: mutations could lead to impossible penetration
Sperm requirements
Sufficient number, motility, morphology
Capacitation: acquire ability to undergo acrosome rxn
Binds ZP3
Fertilization steps
Ovulation Sperm deposition Sperm capacitance Binding to ZP Acrosome rxn Sperm-oocyte fusion Oocyte activation Male/female pronuclei formation
Acrosome reaction
Membrane fusion and exocytosis
Release of hyalurdonidase and acrosin
Sperm-oocyte fusion and oocyte reaction
Fusion mediated by fertilin
Calcium plays large role
Zona reaction leads to cortical granule release and changes ZP3 which are now not capable of binding sperm
Completion of fertilization
Second meiotic divsion/polar body
Pronuclei formation
Polar bodies still visible
Oocyte activation
First meiotic division completed upon LH surge
Meiosis I arrested in prOphase I until Ovulation
Fert/reawakening results in second meiotic division
Meiosis II arrested in METaphase II until MET sperm
Early blastocyst and chr screening
Still has thin zona pellucida
Trophoblast (not inner cell mass) is biopsied for chr/genetic abnormalities
Can also screen anuplodies
Can’t always account for mosaicism
Some places have started using polar body (no info on male, bad for AR phenotypes)
Semen analysis Volume Concentration Motility Morphology
Volume: >1.5ml Concentration: >15x10^6 Motility: >32% Morphology: 4% normal (Based on population of fertile men, not all pop based)
Problems on semen analysis:
CF
Testosterone
CF: no sperm, secretions clog and degenerate vas
T: decrease sperm count, use as contraceptive?
Need to repeat a few months apart
Female evaluation of fertility
How many eggs remaining Fertility = quantity and quality Blood tests: E2, FSH (increases with age), check beginning of cycle AMH (any time) US: check eggs in ovary Can't check blood on OCP
Increasing maternal age
Proportion of euploid embryos declines with age
Large drop late 30’s approaching 40
Role of progesterone
Secreted by corpus luteum (maintained initally by ßhCG from blastocyst)
Triggers decidualization via cAMP
Decidua: characteristics and layers
Accumulation of glycogen and lipid
PRL, IGF1BP, and PGE2 (via COX2) production
Recruitment of dNK cells
Basalis, capsularis, parietalis (eventually uterine cavity is abolished as cap and par come into contact)
Factors that ready endometrium
Prime time: day 20-24 of menstrual cycle
Decreased E2 -> decreased proliferation
Decidua formation/consolidation
Stages of implantation:
Apposition: interdigitation of microvili, pinopod binding
Attachment: actual binding of blastocyst and epi
Invasion: triggers pronounced decidualization
decidua closes behind blastocyst
Normal implantation sites
Abnormal implantation
Usually posterior uterine, near fundus
Placenta previa: covers cervix
Placenta accreta: implants further in wall, post C-section
Ectopic implantation: most common is tube/ampulla
Prevention of immune attack on fetus
Syncytiotrophoblasts: no MHC
Extravilious trophoblast: HLA-C,G, E
Therefore no large influx of B/T cells
HLA-G may downregulate?
Prevention of immune attack on fetus
Syncytiotrophoblasts: no MHC
Extravilious trophoblast: HLA-C,G, E
Therefore no large influx of B/T cells
HLA-G may downregulate?
hCG detection
Embryo: Cycle day 18
Maternal blood: 3 weeks (day 21)
Maternal urine: 4 weeks (day 28)
hCG detection (produced by?)
Normal rise
Ectopic rise
Produced by trophoblast
Embryo: Cycle day 18
Maternal blood: 3 weeks after cycle day 1
Maternal urine: 4 weeks after cycle day 1
Doubles every 48 hours
Ectopic: faster than expected rise
Ectopic: levels >1500-2000 w/out uterine presence
Heterotopic pregnancy
More common with IVF
Mixed uterine and ectopic pregnancy
Ectopic treatment
Methotrexate - targets dividing cells
Surgical: otomy vs. oscopy
Expectant: if hCG is declining on own (rare)
